The incredible advancements in microchip technology have transformed today’s smartphones into devices that would have been considered supercomputers in the early 1990s. However, with the increasing prevalence of artificial intelligence and the Internet of Things, there is a growing demand for a new generation of microchips that not only exceed previous standards of miniaturization and performance but also demonstrate enhanced energy efficiency.
Berkeley Lab scientists have embarked on a mission to revolutionize the transistor, a crucial component of computer microchips, to achieve superior performance and energy efficiency. Their recent work has showcased the potential of new transistor materials utilizing negative capacitance, a unique property that allows for more efficient memory and logic devices.
By harnessing the capabilities of materials with negative capacitance, storing a greater amount of electrical charge at lower voltages becomes possible, presenting a paradigm shift from conventional capacitive materials.
The development of an atomistic understanding of the origins of negative capacitance by a multidisciplinary research team has opened up new possibilities for enhancing and customizing this phenomenon for specific device applications. The team made this advance possible through the use of FerroX, an open-source 3D simulation framework custom-designed for the study of negative capacitance.
This work marks a significant milestone in a multiyear project funded by the Department of Energy in 2021, aiming to design new microchips that outperform conventional silicon chips while requiring less energy.
Berkeley Lab’s co-design approach to microelectronics research, which tightly integrates the atomistic understanding of material properties with specific device requirements, holds the potential to accelerate the pathway from R&D to commercialization by fostering interdisciplinary team science and aligning research aims with all aspects of device development.
“There’s a lot of trial and error in the making of new materials. It’s like making a new recipe. Researchers typically have to work days and nights in the lab to change that recipe. But with our modeling tool, FerroX, you can use your own computer to target specific parameters that can affect the performance of the negative capacitance effect,” said Zhi (Jackie) Yao, a research scientist in Berkeley Lab’s Applied Mathematics & Computational Research Division and senior author on the study.
In 2008, Sayeef Salahuddin, a professor at UC Berkeley and senior scientist at Berkeley Lab, introduced the concept of negative capacitance, offering a new path to energy-efficient computer design. The negative capacitance effect has been discovered in thin films of ferroelectric hafnium oxide and zirconium oxide (HfO2-ZrO2), leading to the development of record-breaking microcapacitors.
To further understand and maximize the potential of negative capacitance, a team led by Yao and Kumar created FerroX, an open-source framework for 3D phase-field simulations of ferroelectric thin films. This allowed them to explore and manipulate the phase composition’s impact on the films’ electronic properties.
“Our goal was to understand the origin of negative capacitance in these films, which is not well understood,” Kumar said. “Our simulations are the first to help researchers tailor a material’s properties for further improvements in negative capacitance observed in the lab.”
The researchers at Berkeley Lab discovered that by optimizing the domain structure, specifically by reducing the size of the ferroelectric grains and arranging them in a particular direction of ferroelectric polarization, the negative capacitance effect could be enhanced.
“This approach to enhancing negative capacitance was unknown before our study because previous models lacked the scalability to easily explore the design space and lacked physics customization,” Yao said.
However, with new modeling capabilities, they were able to explore the design space and customize the physics to achieve this enhancement. This was made possible through collaboration with materials scientists at Berkeley Lab and access to the Perlmutter supercomputer at the Department of Energy’s National Energy Research Scientific Computing Center (NERSC).
The team relied heavily on Perlmutter to develop FerroX, an open-source framework that allows for complex simulation, data analytics, and artificial intelligence experiments. This framework is now available to other researchers and is portable from laptops to supercomputers, offering exciting possibilities for the broader research community.
While the current study simulated the origin of negative capacitance as it evolves at the transistor gate, the team plans to further utilize FerroX to simulate the entire transistor in future studies.
“Over the years, we have made significant progress in both the physics of negative capacitance and integrating that physics into real microelectronics devices,” said Salahuddin. “With FerroX, we can now model these devices starting from atoms, and that will allow us to design microelectronics devices with optimal negative capacitance performance. That would not have been possible without the strength of this co-design group of researchers spanning computing sciences and materials sciences.”
Journal reference:
- Prabhat Kumar, Michael Hoffmann, Andy Nonaka, Sayeef Salahuddin, Zhi (Jackie) Yao. 3D Ferroelectric Phase Field Simulations of Polycrystalline Multi-Phase Hafnia and Zirconia Based Ultra-Thin Films. Advanced Electronic Materials, 2024; DOI: 10.1002/aelm.202400085